Electromagnetic rabbling mechanism for continuously pouring molten metal

ABSTRACT

An electromagnetic rabbling mechanism associated with continuously poured molten metal forming an ingot comprises an inductor coil mounted on a stationary annular laminated magnetic structure providing a rotating magnetic field which surrounds the slowly descending column of solidifying metal and induces rotation of the central and still liquid metal within the solidified outer crust portion of the ingot. Cooling of the inductor coil and its rotary magnetic field producing structure is effected by immersion thereof within a water-filled annular tank co-axially surrounding the descending metal column, the water or other liquid coolant being continuously circulated through the tank along a path designed to establish an optimum amount of heat transfer contact surfaces with all exposed parts of the magnetic structure and the coil.

United States Patent Delassus [451 Sept. 16, 1975 ELECTROMAGNETICRABBLING MECHANISM FOR CONTINUOUSLY POURING MOLTEN METAL [75] Inventor:Jean Delassus, Montmorency.

France [73] Assignee: Compagnie Electro-Mecanique, Paris, France 122]Filed: Dec. 6, 1973 [21] Appl. No.: 422,128

[30] Foreign Application Priority Data Dec. 21. 1972 France 72.45725 7 IIt "14pm 4 "1 g [52] US. Cl. 164/147; 164/250; 335/300 [51] Int. Cl?B22D 11/12; B22D 27/02 [58] Field of Search 164/49, I47, 250, 251.164/273 R; 335/300 [56] References Cited UNITED STATES PATENTS 2,877,5253/1959 Schaaber 164/49 3,056,071 9/1962 Baker et al. 335/300 PrimaryExaminer-Robert D. Baldwin Attorney, Agent, or Firm-Pierce, Scheffler &Parker 5 7 ABSTRACT An electromagnetic rabbling mechanism associatedwith continuously poured molten metal forming an ingot comprises aninductor coil mounted on a stationary annular laminated magneticstructure providing a rotating magnetic field which surrounds the slowlydescending column of solidifying metal and induces rotation of thecentral and still liquid metal within the solidified outer crust portionof the ingot. Cooling of the inductor coil and its rotary magnetic fieldproducing structure is effected by immersion thereof within awater-filled annular tank co-axially surrounding the descending metalcolumn, the water or other liquid coolant being continuously circulatedthrough the tank along a path designed to establish an optimum amount ofheat transfer contact surfaces with all exposed parts of the magneticstructure and the coil.

8 Claims, 5 Drawing Figures PATENTED SEP 1 6 I975 SHEET 3 BF 3ELECTROMAGNETIC RABBLING MECHANISM FOR CONTINUOUSLY POURING MOLTEN METALThe present invention relates to mechanisms for continuously pouringmolten metals and wherein the ingot 5 leaving the ingot mold where itwas shaped continuously descends at a constant and very low speed, theingot then consisting of an outer crust already solidified at the moldexit and of a central, still liquid part, called the molten well orshaft, ofwhich the cross-section progressively narrows during ingotdescent into a so-called secondary cooling zone.

It is known that by setting this liquid metal in motion during itssolidification, a technique known as rabbling, the structure andhomogeneity of the solidified product will be improved; proposalsalready have been advanced to make use of a rotating magnetic field tostir and cause the liquid column to revolve at moderate speed about thelongtitudinal pouring axis.

Such a rotary magnetic field may be achieved by means of a woundmagnetic toroid, which functions as an inductor, of the type used in thestators for electric rotating field motors, with a hollowed central parttraversed by the ingot being solidified and transversely crossed by therotating magnetic field.

However, a magnetic toroid is subjected to the in tense radiation fromthe partially solid ingot still at very high temperature and passingthrough said toroid, which therefore is in danger of being very rapidlyde stroyed unless effective means are provided to ensure its cooling.

To that end, and in conformity with the present invention, adequatecooling is ensured by completely immersing the toroidal inductor in atank subjected to strong circulation of a liquid coolant preferablywater; in order to achieve this result, the magnetic toroid is mountedin an impermeable annular tank provided with a cooling water inlet andan outlet for the water having provided the cooling, the tank being sodesigned, that the water will first circulate from top to bottom throughan annular passage provided between the outer wall of the tank and theperiphery of the stack of annular laminations comprising along theirinner rims the slots holding the inductor winding, then horizontally andradially inward around the conductors at the lower winding heads, thenfrom the bottom towards the top through these winding slots and throughthe narrow annular passage provided between the lower rim of thelamination stack and the inner tank wall, and lastly horizontally andradially outward above the stack around the conductors at the upperwinding heads and out through the outlet.

To prevent that the winding conductors be degraded by the cooling water,they consist of a flexible conductor comprising a central strandedconductor covered by an insulator impermeable to water; one may forinstance use a flexible conductor structure of circular cross-sectionand 6mm in diameter, comprising a 3 mm copper core; while such conductorwill not efficiently fill the slots, they do allow obtaining the desiredfield intensity and ensure effective cooling water passage be tween themin the remaining clear spaces between their cylindrical walls, eventhough they are adjoining.

Another difficulty consists in achieving conductor cable lead-outs thatare impermeable with respect to the cooling water; to that end, and inconformity with a characteristic of the present invention, the lead-outsare solid conductors traversing an insulating plate provided in the wallof the tank and connected inside the latter to the carefully insulatedends of the winding.

In order to ensure the desired hermeticity and insulation of theconnections between the ends of the cables and those of the solid andmassive conductors, the bared cable ends will be soldered into boresfashioned in the solid and massive conductors. heat-setting sleevessurrounding the cable ends and the corresponding ones of the solidconductors, the whole being immersed in a filling resin or pottingcompound inside an insulating sleeve of which the outer rim is sunk in acorresponding groove made to that end in the lower side of theinsulating plate; furthermore, the solid and massive conductors areprovided with an inner shoulder which is pressed against an interposedtoroidal seal against the lower side of the insulating plate by means ofa tightening screw.

Lastly, the tank is so designed that it may be easily dismantled topermit inside cleaning and to provide easy access to the cables andconnections.

The accompanying drawings illustrate a preferred embodiment of thepresent invention wherein:

FIG. 1 is a vertical cross-section of the electromagnetic rabblingmechanism for the continuous pouring of a molten metal;

FIG. 2 is a top view of a cross-section along line llll of FIG. 1',

FIG. 3 is a diametrical section of the electromagnetic mechanism beingused;

FIG. 4 is a section along line lVlV of FIG. 3; and

FIG. 5 is a cross-section on a larger scale, of the winding cableterminals.

With reference now to FIG. 1, the column of molten metal leaving a ladle(not shown) and which descends slowly along a vertical path comprisesfirst an already solid part of ingot 1 within which liquid metal 2 formsa fusion well or shaft; the ingot passes through the interior hollowpart of an annular tank 3 within which is mounted an inductor coil Lwith lower and upper heads 6 and 7 resp., in the circumferentiallyspaced slots 5 of an annular magnetic lamination stack 4.

Cooling water flowing in the tank from top to bottom passes throughinlet 8 and reaches tank 3; it then passes between the outer rim of theannular lamination stack 4 and the outer wall 9 of tank 3 to the lowerpart of the tank, then flows horizontally radially inward while coolingthe lower winding heads 6, next moving from bottom to top in slots 5 oflamination stack 4 and also in the annular clear space 10 left betweenthe inner rim of the annular lamination stack 4 and inner wall 11 of thetank, and lastly horizontally and radially outward at the upper tankpart, where it cools the conductors of the upper winding heads 7, andfinally discharges through outlet 12.

FIG. 3 shows in greater detail several radial passages 14 in the lowerclamping plate 13 of lamination stack 4, which supply cooling water tothe center and direct it towards the winding terminals 6 throughorifices 15 designed for that purpose; the figure also shows the radialspaces 16 provided between plates separating the various winding heads 6from one another; similarly, as regards the upper part of the tank,after the water has come up through slots 5 holding the conductorwinding and through space 10 between the inner surface of laminationstack 4 and inner wall 11 of the tank, it will cool the upper windingheads 7, passing through the radial 3 spaces 19 between the platesseparating the several upper winding heads 7, then discharging throughoutlet 12. Direct through-holes 17 of small diameter and drilled inupper clamping plate 18 prevent formation of air pockets in the upperannular space between tank 9 and lamination stack 4.

The annular tank 3 is sectionalized in order to permit easy access tothe space between the inner and outer walls for inspection of theelectrical components as well as to facilitate cleaning of the interiorof the tank. For this purpose the inner wall ll is continuous from thetop to the bottom. but the outer wall 9 is divided into upper and lowersections joined together by means of connection flanges provided withsealing rings 22 therebetween and which are fastened by means of circumferentially spaced bolt-and-nut connections 20. The upper end of theouter wall 9 terminates in a radially inward wall reaching to the innerwall 11 and which is joined to the latter by means of a sealing ring 23and circumferentially spaced connection screws 21. Upon removal of theconnection bolts and screws 21, the upper part of the tank may be liftedoff, thereby providing full access to the interior of the tank.

In order to achieve good electrical insulation simultaneously withsatisfactory hermeticity with respect to the cooling water. the windingconductor lead-outs may be designed in the manner shown in FIGS. 4 and5, namely. as solid and massive conductors 24 which traverse aninsulating plate 25 installed in a junction neck 26 extending outwardfrom the tank 3 as illustrated in FIG. 4. As illustrated in a largerscale in FIG. 5, each of the massive conductor parts 24 includes bores29 in the upper portions 30 for receiving and sol dering the bared ends27 of the flexible inductor con ductors 28, hermeticity of the assemblybeing achieved by means of heat-shrinking sleeves 31; the whole isimmersed in a potting resin 32 inside a circular insulating sleeve 33 ofwhich the end 34 is pushed into a circular groove in insulating plate25', a tightening nut 35 screwed onto a threaded stern portion of theconductor part 24 clamps the integrated set of cable lead-outs 28 toinsulating plate 25 by compressing a toroidal seal ring 36 whichprovides the desired hermeticity; cablelugs 37 may thereafter betightened by nuts 38.

While the embodiment of the invention described herein and referring tothe accompanying drawings is preferred, it is considered illustrativeonly and hence verious modifications may be resorted to without therebydeparting from the scope of the appended claims.

I claim:

1. A liquid-cooled electromagnetic rabbling mecha nism associated with acontinuously poured and descending column of molten metal forming aningot which comprises an annular cooling tank adapted to co-axiallysurround the descending column of metal an annular laminated magneticstructure located coaxially within said cooling tank and having acylindric array of axially extending coil-receiving slots located at theinner periphery thereof, an inductor coil located in said slots, saidinductor coil being constituted by a winding of an electrical conductorcovered by a sheath which is impermeable to the liquid coolant, alead-out structure from the terminal ends of said coil through the wallof said cooling tank to an energizing source thereby enabling productionof a rotating magnetic field which induces rotation of the centrallylocated and still molten metal within the outer crust portion of theingot being formed, and means for effecting forced circulation of aliquid coolant through said tank which includes means establishing aflow path therefor which provides passage of the coolant from an inletdownwardly through an annular passage provided between the outer wall ofsaid tank and the outer periphery of said annular magnetic structure tothe bottom of the coil. thence inwardly to the inner periphery of saidannular magnetic structure. thence upwardly through said slots and anannular passage provided between the inner periphery of said annularmagnetic structure and the inner wall of said tank to the top of thecoil, and thence outwardly from said tank through a discharge outlet.

2. A liquid-cooled electromagnetic rabbling mechanism as defined inclaim 1 wherein said annular laminated magnetic structure includesclamping plates at the upper and lower ends thereof, said lower clampingplate including radially extending passages therein for directling theliquid coolant radially inward to the inner periphery of said annularmagnetic structure and said upper clamping plate including amultiplicity of through-holes to prevent formation of air pockets in theupper annular space between said tank and said annular laminatedmagnetic structure.

3. A liquid-cooled electromagnetic rabbling mechanism as defined inclaim 1 wherein the conductor from which said inductor coil is wound hasa flexible characteristic and is constituted by stranded cable coveredby the sheath of material impermeable to the liquid coolant.

4. A liquid-cooled electromagnetic rabbling mecha nism as defined inclaim 3 wherein said flexible stranded cable which forms the coilconductor has a circular cross-section of 6mm in diameter and includes a3 mm diameter copper core.

5. A liquid-cooled electromagnetic rabbling mechanism as defined inclaim I wherein said tank includes a junction neck and a transverselyextending insulator plate therein through which are passed and supportedthe lead-out terminal structures for the various parts of said inductorcoil.

6. A liquid-cooled electromagnetic rabbling mecha' nism as defined inclaim 5 wherein the lead-out structures for the various conductormembers of said inductor coil include massive parts of conductivematerial including bores for receiving and connection by soldering ofthe bared ends of the conductor parts. heat shrinkable sleeves enclosingand sealing off the connections between the conductor ends and saidbored massive parts, said sealed-off connections being immersed in apotting resin and covered by an insulating sleeve the end of which isembedded in a corresponding groove provided in said insulator plate.

7. A liquid-cooled electromagnetic rabbling mechanism as defined inclaim 6 wherein said massive conductor part includes a threaded stemportion projecting through said insulator plate and secured thereto by aout, said stern portion establishing a shouldered portion and a sealingring surrounding said stem portion and which forms a seal between saidshouldered portion and the adjacent surface of said insulator plate.

8. A liquid-cooled electromagnetic rabbling mechanism as defined inclaim 1 wherein said annular tank is sectionalized into upper and lowerparts which are disconnectible to permit removal of the upper part foraccess to the interior of the tank.

1. A liquid-cooled electromagnetic rabbling mechanism associated with acontinuously poured and descending column of molten metal forming aningot which comprises an annular cooling tank adapted to co-axiallysurround the descending column of metal, an annular laminated magneticstructure located co-axially within said cooling tank and having acylindric array of axially extending coil-receiving slots located at theinner periphery thereof, an inductor coil located in said slots, saidinductor coil being constituted by a winding of an electrical conductorcovered by a sheath which is impermeable to the liquid coolant, alead-out structure from the terminal ends of said coil through the wallof said cooling tank to an energizing source thereby enabling productionof a rotating magnetic field which induces rotation of the centrallylocated and still molten metal within the outer crust portion of theingot being formed, and means for effecting forced circulation of aliquid coolant through said tank which includes means establishing aflow path therefor which provides passage of the coolant from an inletdownwardly through an annular passage provided between the outer wall ofsaid tank and the outer periphery of said annular magnetic structure toThe bottom of the coil, thence inwardly to the inner periphery of saidannular magnetic structure, thence upwardly through said slots and anannular passage provided between the inner periphery of said annularmagnetic structure and the inner wall of said tank to the top of thecoil, and thence outwardly from said tank through a discharge outlet. 2.A liquid-cooled electromagnetic rabbling mechanism as defined in claim 1wherein said annular laminated magnetic structure includes clampingplates at the upper and lower ends thereof, said lower clamping plateincluding radially extending passages therein for directling the liquidcoolant radially inward to the inner periphery of said annular magneticstructure and said upper clamping plate including a multiplicity ofthrough-holes to prevent formation of air pockets in the upper annularspace between said tank and said annular laminated magnetic structure.3. A liquid-cooled electromagnetic rabbling mechanism as defined inclaim 1 wherein the conductor from which said inductor coil is wound hasa flexible characteristic and is constituted by stranded cable coveredby the sheath of material impermeable to the liquid coolant.
 4. Aliquid-cooled electromagnetic rabbling mechanism as defined in claim 3wherein said flexible stranded cable which forms the coil conductor hasa circular cross-section of 6mm in diameter and includes a 3 mm diametercopper core.
 5. A liquid-cooled electromagnetic rabbling mechanism asdefined in claim 1 wherein said tank includes a junction neck and atransversely extending insulator plate therein through which are passedand supported the lead-out terminal structures for the various parts ofsaid inductor coil.
 6. A liquid-cooled electromagnetic rabblingmechanism as defined in claim 5 wherein the lead-out structures for thevarious conductor members of said inductor coil include massive parts ofconductive material including bores for receiving and connection bysoldering of the bared ends of the conductor parts, heat shrinkablesleeves enclosing and sealing off the connections between the conductorends and said bored massive parts, said sealed-off connections beingimmersed in a potting resin and covered by an insulating sleeve the endof which is embedded in a corresponding groove provided in saidinsulator plate.
 7. A liquid-cooled electromagnetic rabbling mechanismas defined in claim 6 wherein said massive conductor part includes athreaded stem portion projecting through said insulator plate andsecured thereto by a nut, said stem portion establishing a shoulderedportion and a sealing ring surrounding said stem portion and which formsa seal between said shouldered portion and the adjacent surface of saidinsulator plate.
 8. A liquid-cooled electromagnetic rabbling mechanismas defined in claim 1 wherein said annular tank is sectionalized intoupper and lower parts which are disconnectible to permit removal of theupper part for access to the interior of the tank.